Re: [PATCH 09/11] bpf: Add d_path helper

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	Martin KaFai Lau <kafai@fb.com>, David Miller <davem@redhat.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Wenbo Zhang <ethercflow@gmail.com>,
	KP Singh <kpsingh@chromium.org>, Andrii Nakryiko <andriin@fb.com>,
	Brendan Gregg <bgregg@netflix.com>,
	Florent Revest <revest@chromium.org>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH 09/11] bpf: Add d_path helper
Date: Fri, 19 Jun 2020 11:25:27 -0700	[thread overview]
Message-ID: <CAEf4BzZDCtW-5r5rN+ufZi1hUXjw8QCF+CiyT5sOvQQEEOqtiQ@mail.gmail.com> (raw)
In-Reply-To: <20200619133124.GJ2465907@krava>

On Fri, Jun 19, 2020 at 6:31 AM Jiri Olsa <jolsa@redhat.com> wrote:
>
> On Thu, Jun 18, 2020 at 09:35:10PM -0700, Andrii Nakryiko wrote:
> > On Tue, Jun 16, 2020 at 3:07 AM Jiri Olsa <jolsa@kernel.org> wrote:
> > >
> > > Adding d_path helper function that returns full path
> > > for give 'struct path' object, which needs to be the
> > > kernel BTF 'path' object.
> > >
> > > The helper calls directly d_path function.
> > >
> > > Updating also bpf.h tools uapi header and adding
> > > 'path' to bpf_helpers_doc.py script.
> > >
> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > > ---
> > >  include/linux/bpf.h            |  4 ++++
> > >  include/uapi/linux/bpf.h       | 14 ++++++++++++-
> > >  kernel/bpf/btf_ids.c           | 11 ++++++++++
> > >  kernel/trace/bpf_trace.c       | 38 ++++++++++++++++++++++++++++++++++
> > >  scripts/bpf_helpers_doc.py     |  2 ++
> > >  tools/include/uapi/linux/bpf.h | 14 ++++++++++++-
> > >  6 files changed, 81 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > index a94e85c2ec50..d35265b6c574 100644
> > > --- a/include/linux/bpf.h
> > > +++ b/include/linux/bpf.h
> > > @@ -1752,5 +1752,9 @@ extern int bpf_skb_output_btf_ids[];
> > >  extern int bpf_seq_printf_btf_ids[];
> > >  extern int bpf_seq_write_btf_ids[];
> > >  extern int bpf_xdp_output_btf_ids[];
> > > +extern int bpf_d_path_btf_ids[];
> > > +
> > > +extern int btf_whitelist_d_path[];
> > > +extern int btf_whitelist_d_path_cnt;
> >
> > So with suggestion from previous patch, this would be declared as:
> >
> > extern const struct btf_id_set btf_whitelist_d_path;
>
> yes
>
> SNIP
>
> > >  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > >   * function eBPF program intends to call
> > > diff --git a/kernel/bpf/btf_ids.c b/kernel/bpf/btf_ids.c
> > > index d8d0df162f04..853c8fd59b06 100644
> > > --- a/kernel/bpf/btf_ids.c
> > > +++ b/kernel/bpf/btf_ids.c
> > > @@ -13,3 +13,14 @@ BTF_ID(struct, seq_file)
> > >
> > >  BTF_ID_LIST(bpf_xdp_output_btf_ids)
> > >  BTF_ID(struct, xdp_buff)
> > > +
> > > +BTF_ID_LIST(bpf_d_path_btf_ids)
> > > +BTF_ID(struct, path)
> > > +
> > > +BTF_WHITELIST_ENTRY(btf_whitelist_d_path)
> > > +BTF_ID(func, vfs_truncate)
> > > +BTF_ID(func, vfs_fallocate)
> > > +BTF_ID(func, dentry_open)
> > > +BTF_ID(func, vfs_getattr)
> > > +BTF_ID(func, filp_close)
> > > +BTF_WHITELIST_END(btf_whitelist_d_path)
> >
> > Oh, so that's why you added btf_ids.c. Do you think centralizing all
> > those BTF ID lists in one file is going to be more convenient? I lean
> > towards keeping them closer to where they are used, as it was with all
> > those helper BTF IDS. But I wonder what others think...
>
> either way works for me, but then BTF_ID_* macros needs to go
> to include/linux/btf_ids.h header right?
>

given it's internal API, I'd probably just put it in
include/linux/btf.h or include/linux/bpf.h, don't think we need extra
header just for these


> jirka
>
> >
> > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > > index c1866d76041f..0ff5d8434d40 100644
> > > --- a/kernel/trace/bpf_trace.c
> > > +++ b/kernel/trace/bpf_trace.c
> > > @@ -1016,6 +1016,42 @@ static const struct bpf_func_proto bpf_send_signal_thread_proto = {
> > >         .arg1_type      = ARG_ANYTHING,
> > >  };
> > >
> >
> > [...]
> >
>